1. Field of the Invention
The present invention relates to an elastomer compound used to slowly dispense a fertilizer compound or other desired substance into a targeted environment over a period of time. More particularly, the present invention relates to such elastomer compounds where the desired substance is dissolved within the elastomer compound, at a supersaturated concentration, causing the desired substance to slowly bloom to the surface of the elastomer compound and be dispensed into the surrounding environment.
2. Description of the Prior Art
Bloom is a term of art in elastomers that refers to the migration of a liquid or solid material from the composition of the elastomer to the surface of the elastomer. Bloom is caused when a dissolved ingredient is added to the elastomer compound recipe in a concentration that is in excess of its solubility. In such a situation, if the conditions for crystallization of the supersaturated ingredient are more favorable in the presence of air than within the body of the elastomer, then the supersaturated ingredient will separate out of the elastomer compound and crystallize at the surface of the polymer as it contacts the surrounding air. The change in the saturation concentration gradient created by the surface crystallization causes the supersaturated ingredient to migrate from within the elastomer compound toward the exterior surfaces of the elastomer compound. The bloom of the supersaturated ingredient will continue over time until the concentration of the blooming ingredient within the elastomer compound falls to a concentration corresponding to the saturation point of the elastomer compound. Bloom ceases when the concentration of the migrating substance in the elastomer compound becomes equal to its solubility at a given temperature.
The slow dispensing of a chemical compound, over a prolonged period of time, is a useful process in many industries. One of the most obvious of these industries is that of agriculture. Dispensing fertilizers and/or pesticides on plants is often an expensive and labor intensive operation. Additionally, conventional applications of fertilizer and pesticides must be repeated because the potency of such compounds is often time sensitive. Furthermore, environmental factors such as rain may wash such compounds away from the plants before they have had an opportunity to perform their intended function. Additionally, too much fertilizer or pesticide may have an adverse effect on plants by causing fertilizer burn or adding unacceptable levels of poisons to the fruit born by such plants.
In an attempt to reduce the time and labor involved with dispensing fertilizer and pesticides to plants, the prior art has seen the development of slow dispensing devices, whereby upon one application, small amounts of fertilizer or pesticides are made available to plants over an extended period of time. In the prior art, such slow dispensing devices typically include a biodegradable material impregnated with a fertilizer or pesticide product. As the biodegradable material decomposes, the fertilizer and/or pesticide is released into the surrounding soil. Such prior art devices are exemplified by U.S. Pat. No. 3,320,695 to Moore, Jr., entitled DEGRADABLE POLYOLEFIN MULCHING FILM, U.S. Pat. No. 1,554,865 to Magoon, entitled DEVICE FOR TREATING SOIL and U.S. Pat. No. 4,063,919 to Grano, Jr., entitled FERTILIZER RODS.
The problems associated with such biodegradable fertilizer dispensing devices is that they are time consuming and labor intensive to install around plants. Furthermore, the amount of fertilizer or pesticide released by such devices is dependent entirely upon the environment in which they contact. For instance, if such devices were positioned in rich soil that had a high moisture content and a high bacterial presence, the prior art devices would decompose very rapidly and the fertilizer or pesticide released would not last throughout the entire growing season. Adversely, if such devices were positioned on dry soil with a very low moisture content and bacterial presence, the prior art devices may not adequately decompose and therefore may not properly dispense the fertilizer or pesticide.
In other prior art products, the osmotic effect of water passing through a fertilizer or pesticide containing medium is used to dispense the fertilizer or pesticide around desired plants. One such prior art device is taught by U.S. Pat. No. 4,224,048 to Pendergast, entitled OSMOTIC FERTILIZER PRODUCT AND FERTILIZATION METHOD. In the Pendergast patent, a fertilizer is shown impregnated within a water swellable polymer. The polymer absorbs water administered to the plant, dilutes fertilizer into the water and passes the water/fertilizer solution on to the plant with a controlled capillary action. The disadvantage of this design is that the water swellable polymer must be buried under the soil near each plant. For this reason, the application of the water swellable polymer is highly labor intensive. Additionally, with the use of a water swellable polymer, the dispensing of fertilizer is directly proportional to the moisture content of the soil. If the moisture content is high, osmosis occurs and large amounts of fertilizer are released. Adversely, if the soil has a very low moisture content, almost no fertilizer is released to the plant.
In U.S. Pat. No. 5,105,577 to Hedges, entitled ARTIFICIAL MULCH CHIPS, a thermoplastic material is shown with a textured surface. The thermoplastic material is then coated with an active ingredient, such as an insecticide, and is thrown upon the soil in the region of a garden. Once in the garden, the effects of wind and water cause diffusion of the active ingredient into the surrounding environment. No mechanism is provided to control the rate of diffusion of the active ingredient over time.
In U.S. Pat. No. 4,166,340 to Pluenneke, entitled POT LINING METHOD WITH RECLAIMED TIRE FIBERS, a polymer is used to enhance the quality of soil without the addition of a fertilizer compound. In the Pluenneke patent, shreds of an automotive tire are used in the bottom of a potted plant. The tire pieces provide good drainage characteristics and provide micronutrients of sulphur, iron, zinc and manganese to the plant. The tire pieces must be buried proximate the roots of a plant, as such the process is highly time consuming and labor intensive.
Although the prior art does show the use of various elastomer products in the controlled dispensing of fertilizers and pesticides, the prior art fails to show fertilizers or pesticides dissolved within the elastomer such that the added fertilizer or pesticide supersaturates the elastomer compound and blooms to the exterior of the elastomer over a known period of time. Such a migration of fertilizer or pesticide to the exterior of the elastomer compound is not dependent upon available moisture in the soil or the bacterial content of the soil. Consequently, fertilizer or pesticide can be slowly and consistently dispensed over a period of time regardless of the environment surrounding the plant.
It is a further object of the present invention to produce a product that can be administered around plants above the soil, thereby reducing the labor involved in supplying fertilizers to plants.